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Reports on Progress in Physics

N David Mermin
We still lack any consensus about what one is actually talking about
 as one uses quantum mechanics. There is a gap between the abstract terms in
 which the theory is couched and the phenomena the theory enables each of us to
 account for so well. Because it has no practical consequences for how we each
 use quantum mechanics to deal with physical problems, this cognitive dissonance
 has managed to coexist with the quantum theory from the very beginning. The
 absence of conceptual clarity for almost a century suggests that the problem might
 lie in some implicit misconceptions about the nature of scientic explanation that
 are deeply held by virtually all physicists, but are rarely explicitly acknowledged...
September 20, 2018: Reports on Progress in Physics
Subir Sachdev
This review describes how topological order associated with the presence of emergent gauge elds can reconstruct Fermi surfaces of metals, even in the absence of translational symmetry breaking. We begin with an introduction to topological order using Wegner's quantum Z2 gauge theory on the square lattice: the topological state is characterized by the expulsion of defects, carrying Z2 magnetic 
 ux. The interplay between topological order and the breaking of global symmetry is described by the non-zero temperature statistical mechanics of classical XY models in dimension
 D = 3; such models also describe the zero temperature quantum phases of bosons with
 short-range interactions on the square lattice at integer lling...
September 13, 2018: Reports on Progress in Physics
Ran Adler, Chang-Jong Kang, Chuck-Hou Yee, Gabriel Kotliar
Included in pdf file of the article.
August 23, 2018: Reports on Progress in Physics
Robert P Behringer, B Chakraborty
Granular materials consist of macroscopic grains, interacting via contact forces, and unaffected by thermal fluctuations. They are one of a class systems that undergo jamming, i.e. a transition between fluid-like and disordered solid-like states. Roughly twenty years ago, proposals by Cates et al. for the shear response of colloidal systems and by Liu and Nagel, for a universal jamming diagram in a parameter space of packing fraction, $\phi$, shear stress, $\tau$, and temperature, $T$ raised key questions. Contemporaneously, experiments by Howell et al...
August 22, 2018: Reports on Progress in Physics
Matthew D Duez, Yosef Zlochower
We review the dramatic progress in the simulations of compact objects and compact-object binaries that has taken place in the first two decades of the twenty-first century. This includes simulations of the inspirals and violent mergers of binaries containing black holes and neutron stars, as well as simulations of black-hole formation through failed supernovae and high-mass neutron star--neutron star mergers. Modeling such events requires numerical integration of the field equations of general relativity in three spatial dimensions, coupled, in the case of neutron-star containing binaries, with increasingly sophisticated treatment of fluids, electromagnetic fields, and neutrino radiation...
August 17, 2018: Reports on Progress in Physics
Stefano Gariglio, Andrea D Caviglia, Jean-Marc Triscone, Marc Gabay
Within the last twenty years, the status of the spin-orbit interaction has evolved from that of a simple atomic contribution to a key effect that modifies the electronic band structure of materials. It is regarded as one of the basic ingredients for spintronics, locking together charge and spin degrees of freedom and recently it is instrumental in promoting a new class of compounds, the topological insulators. In this review, we present the current status of the research on the spin-orbit coupling in transition metal oxides, discussing the case of two semiconducting compounds, SrTiO<sub>3</sub> and KTaO<sub>3</sub>, and the properties of surfaces and interfaces based on these...
July 30, 2018: Reports on Progress in Physics
Stephan Rachel
The discovery of the quantum spin Hall effect and topological insulators more than a decade ago has revolutionized modern condensed matter physics. Today, the field of topological states of matter is one of the most active and fruitful research areas for both experimentalists and theorists. The physics of topological insulators is typically well described by band theory and systems of non-interacting fermions. In contrast, several of the most fascinating effects in condensed matter physics merely exist due to electron-electron interactions, examples include unconventional superconductivity, the Kondo effect, and the Mott-Hubbard transition...
July 30, 2018: Reports on Progress in Physics
Lucio Mayer, Silvia Bonoli
The direct collapse model for the formation of massive black holes
 has gained increased support as it provides a natural explanation
 for the appearance of bright quasars already less than a billion years from
 the Big Bang. In this paper we review a recent scenario for direct collapse that
 relies on multi-scale gas inflows initiated by the major merger of massive gas-rich
 galaxies at $z > 6$, where gas has already achieved solar composition.
 Hydrodynamical simulations undertaken to explore our scenario show
 that supermassive, gravitationally bound compact gaseous disks weighing a billion solar masses,
 only a few pc in size, form in the nuclei of merger remnants in less than $10^5$ yr...
July 30, 2018: Reports on Progress in Physics
Daryl Inna Vulis, Orad Reshef, Philip Camayd-Munoz, Eric Mazur
Metamaterials with a refractive index of zero exhibit properties that are important for integrated optics. Possessing an infinite effective wavelength and zero spatial phase change, zero-index metamaterials may be especially useful for routing on-chip photonic processes and reducing the footprint of nonlinear interactions. Zero-index has only been achieved recently in an integrated platform through a Dirac-cone dispersion, enabling some of these more exciting applications in an integrated platform. This paper presents an overview of Dirac-cone zero-index metamaterials, including the fundamental physics, history and demonstration in the optical regime, as well as current challenges and future directions...
July 17, 2018: Reports on Progress in Physics
Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya, Isamu Akasaki
This paper describes the status and prospects of gallium nitride-based vertical-cavity surface-emitting lasers (VCSELs) with semiconductor-based distributed Bragg reflectors. These optoelectronic devices which emit laser light from the violet to green region are expected to be a superior light source for next-generation displays and illumination, such as retinal scanning displays and adaptive headlights. The development status and prospects are discussed in comparison with already commercialized gallium arsenide-based infrared VCSELs...
July 17, 2018: Reports on Progress in Physics
Kun Zhao, Thomas G Mason
Advances in both top-down and bottom-up sytheses of a wide variety of complex colloidal building blocks and also in methods of controlling their assembly in solution have led to new and interesting forms of highly controlled soft matter. In particular, top-down lithographic methods of producing monodisperse colloids now provide precise human-designed control over their sub-particle features, opening up a wide range of new possibilities for assembly structures that had been previously limited by the range of shapes available through bottom-up methods...
July 6, 2018: Reports on Progress in Physics
Karl-Heinz Schmidt, Beatriz Jurado
An overview is given on some of the main advances in the experimental methods, experimental results, theoretical models and ideas of the last few years in the field of nuclear fission. New approaches have considerably extended the availability of fissioning systems for the experimental study of nuclear fission, and have provided a full identification of all fission products in A and Z for the first time. In particular, the transition from symmetric to asymmetric fission around 226 Th, some unexpected structures in the mass distributions in the fission of systems around Z  =  80-84, and an extended systematics of the odd-even effect in the fission fragment Z distributions have all been measured (Andreyev et al 2018 Rep...
June 28, 2018: Reports on Progress in Physics
Isabel A Olson, Alexander G Shtukenberg, Bart Kahr, Michael D Ward
Dislocations in molecular crystals remain terra incognita. Owing to the complexity of molecular structure, dislocations in molecular crystals can be difficult to understand using only the foundational concepts devised over decades for hard materials. Herein, we review the generation, structure, and physicochemical consequences of dislocations in molecular crystals. Unlike metals, ceramics, and semiconductors, molecular crystals are often characterized by flexible building units of low symmetry, thereby limiting analysis, complicating modeling, and prompting new approaches to elucidate their role in crystallography from growth to mechanics...
September 2018: Reports on Progress in Physics
S Gales, K A Tanaka, D L Balabanski, F Negoita, D Stutman, O Tesileanu, C A Ur, D Ursescu, I Andrei, S Ataman, M O Cernaianu, L D'Alessi, I Dancus, B Diaconescu, N Djourelov, D Filipescu, P Ghenuche, D G Ghita, C Matei, K Seto, M Zeng, N V Zamfir
The European Strategy Forum on Research Infrastructures (ESFRI) has selected in 2006 a proposal based on ultra-intense laser fields with intensities reaching up to 1022 -1023 W cm-2 called 'ELI' for Extreme Light Infrastructure. The construction of a large-scale laser-centred, distributed pan-European research infrastructure, involving beyond the state-of-the-art ultra-short and ultra-intense laser technologies, received the approval for funding in 2011-2012. The three pillars of the ELI facility are being built in Czech Republic, Hungary and Romania...
September 2018: Reports on Progress in Physics
Thomas Zanon-Willette, Rémi Lefevre, Rémi Metzdorff, Nicolas Sillitoe, Sylvain Almonacil, Marco Minissale, Emeric de Clercq, Alexey V Taichenachev, Valeriy I Yudin, Ennio Arimondo
Probing an atomic resonance without disturbing it is an ubiquitous issue in physics. This problem is critical in high-accuracy spectroscopy or for the next generation of atomic optical clocks. Ultra-high resolution frequency metrology requires sophisticated interrogation schemes and robust protocols handling pulse length errors and residual frequency detuning offsets. This review reports recent progress and perspective in such schemes, using sequences of composite laser-pulses tailored in pulse duration, frequency and phase, inspired by NMR techniques and quantum information processing...
September 2018: Reports on Progress in Physics
Richard J Hill, Peter Kammel, William J Marciano, Alberto Sirlin
Weak capture in muonic hydrogen (μH) as a probe of the chiral properties and nucleon structure predictions of quantum chromodynamics (QCD) is reviewed. A recent determination of the axial-vector charge radius squared, [Formula: see text], from a model independent z expansion analysis of neutrino-nucleon scattering data is employed in conjunction with the MuCap measurement of the singlet muonic hydrogen capture rate, [Formula: see text], to update the induced pseudoscalar nucleon coupling [Formula: see text] derived from experiment, and [Formula: see text] predicted by chiral perturbation theory...
September 2018: Reports on Progress in Physics
Liam Collins, Jason I Kilpatrick, Sergei V Kalinin, Brian J Rodriguez
Fundamental mechanisms of energy storage, corrosion, sensing, and multiple biological functionalities are directly coupled to electrical processes and ionic dynamics at solid-liquid interfaces. In many cases, these processes are spatially inhomogeneous taking place at grain boundaries, step edges, point defects, ion channels, etc and possess complex time and voltage dependent dynamics. This necessitates time-resolved and real-space probing of these phenomena. In this review, we discuss the applications of force-sensitive voltage modulated scanning probe microscopy (SPM) for probing electrical phenomena at solid-liquid interfaces...
August 2018: Reports on Progress in Physics
S A Parameswaran, Romain Vasseur
We review recent developments in the study of out-of-equilibrium topological states of matter in isolated systems. The phenomenon of many-body localization, exhibited by some isolated systems usually in the presence of quenched disorder, prevents systems from equilibrating to a thermal state where the delicate quantum correlations necessary for topological order are often washed out. Instead, many-body localized systems can exhibit a type of eigenstate phase structure wherein their entire many-body spectrum is characterized by various types of quantum order, usually restricted to quantum ground states...
August 2018: Reports on Progress in Physics
Joshua M Deutsch
The emergence of statistical mechanics for isolated classical systems comes about through chaotic dynamics and ergodicity. Here we review how similar questions can be answered in quantum systems. The crucial point is that individual energy eigenstates behave in many ways like a statistical ensemble. A more detailed statement of this is named the eigenstate thermalization hypothesis (ETH). The reasons for why it works in so many cases are rooted in the early work of Wigner on random matrix theory and our understanding of quantum chaos...
August 2018: Reports on Progress in Physics
Claudia Ratti
In the last few years, numerical simulations of Quantum chromodynamics on the lattice have reached a new level of accuracy. A wide range of thermodynamic quantities is now available in the continuum limit and for physical quark masses. This allows a comparison with measurements from heavy ion collisions for the first time. Furthermore, calculations of dynamical quantities are also becoming available. The combined effort from first principles and experiment allows us to gain an unprecedented understanding of the properties of quark-gluon plasma...
August 2018: Reports on Progress in Physics
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